The esophagus is a tubular organ that carries food and liquid from the throat to the stomach. Accurate measurements of physiological parameters of the esophagus under realistic swallowing conditions are valuable in diagnosing esophageal diseases such as Achalasia, dysphagia, diffuse esophageal spasm, ineffective esophageal motility, and hypertensive lower esophageal sphincter (LES). When a person with a healthy esophagus swallows, circular muscles in the esophagus contract. The contractions begin at the upper end of the esophagus and propagate downwardly toward the lower esophageal sphincter (LES). The function of the peristaltic muscle contractions, i.e., to propel food and drinks through the esophagus to the stomach, is sometimes called the motility function, but is also often referred to as peristalsis.
An upper esophageal sphincter (UES) is located at an upper end of the esophagus. The UES is a muscle that serves as a valve between the esophagus and the pharynx from which the esophagus receives food and liquid when swallowing.
The lower esophageal sphincter (LES) is located at a lower end of the esophagus. The LES is a muscle that serves as a valve between the esophagus and the stomach. The LES protects the lower esophagus from stomach acid and bile, which causes the discomfort of heartburn and in time can damage or scar the esophagus.
The LES is normally closed, but it opens momentarily when a peristaltic contraction approaches it to admit any swallowed volume of food or drink, which is called a “bolus,” into the stomach. As a peristaltic contraction passes through each point along the esophagus, the esophageal pressure at that point rises to a maximum and then falls back to a base pressure at the relaxed state. This peristaltic propagation of the esophageal contraction tends to propel the “bolus,” ahead of the point of peak pressure and down the esophagus toward the stomach. The motility function of the esophagus, i.e., the esophagus' ability to move a mass, is dependent on several factors, including the peristaltic pressure profile and the characteristics of the esophageal muscles.
Esophageal pressure measurement, or manometry, as well as electrical impedance have been used to assess motility function of the esophagus and bolus transit dynamics in the esophagus. A typical esophageal manometer includes an elongated catheter or probe with pressure sensors located along its length. The catheter or probe is designed to be inserted into the esophagus, typically reaching the LES and extending into the stomach of a patient, with the pressure sensors positioned at the LES and at a plurality of other specific points along the length of the esophagus at predetermined distances above the LES. During a typical test, the patient swallows a specific amount of water with the manometer placed in the esophagus. The esophageal pressure at the pressure sensors can be measured and used as an indication of the magnitude and sequence of the peristaltic contractions. In addition, because the positions of the sensors are known, the velocity of the peristaltic motion can also be ascertained from the location of the peak pressure, or onset of pressure rise, at each location as a function of time. The test can be repeated a number of times to obtain a set of pressure and velocity values, a statistical analysis of which may be used for diagnostic purposes.
High-resolution manometry involves collection of data with a catheter having closely spaced sensors. Such high-resolution data enables spatiotemporal contour plots visualization of contractile pressure physiology. Products such as ManoScan™ data acquisition software and ManoView™ data analysis software may be used to aid in visualizing high-resolution manometry data.
High-resolution impedance has also been researched independently and also provides for spatiotemporal plotting of bolus movement. Electrical impedance at a plurality of points in the esophagus can be used to detect and monitor movement of a bolus through the esophagus. A bolus of water or food will have different electrical impedance than the non-filled esophagus, so a change in impedance in the esophagus indicates presence of a bolus. Therefore, an elongated probe positioned in the esophagus with a plurality of impedance and/or acidity sensors dispersed along its length can be used to detect and monitor the bolus transit, i.e., the movement of a bolus through the esophagus.